A conventional roll call tester, for example, comprises: a normal cell; a redundancy cell that, together with the normal cell, constitutes a memory cell; and a data amplifier connected to the normal cell and the redundancy cell. The data amplifier receives from the normal cell and the redundancy cell data through a bit line or an I/O line, amplifies the data, and outputs the amplified data to a data bus. A data output circuit is connected to the data amplifier. The data output circuit receives data on the data bus, and outputs the data to a DQ (data input/output) pin. A test signal activation circuit is provided for inputting a roll call test signal into a data amplifier activation circuit. The data amplifier activation circuit outputs the data amplifier activation signal, upon receipt of the test signal, to the data amplifier, and outputs a redundancy detection circuit activation signal to a redundancy detection circuit. A predetermined test signal activation address signal is input into the test signal activation circuit.
The roll call tester further comprises a redundancy circuit comprising FUSEROM (a replacement address setting circuit having a group of fuses). A predetermined address signal is input into FUSEROM. A redundancy selection signal and a normal cell non-selection signal are output from the redundancy circuit. The redundancy selection signal is input into the redundancy cell and a redundancy detection circuit, and the normal cell non-selection signal is input into the normal cell. The redundancy detection circuit outputs a judgment result output signal to the data bus.
The operation of the conventional roll call tester will be explained. Under normal condition other than the roll call test, a predetermined test signal activation address signal is nonactive, so that the test signal activation circuit is nonactive, and a roll call test signal ROLLC is also nonactive. Therefore, the data amplifier activation circuit activates a data amplifier activation signal DAMP to activate the data amplifier, while a redundancy detection circuit activation signal REDTST is rendered nonactive to render the redundancy detection circuit nonactive. When the redundancy circuit has not been activated by predetermined addressing, the redundancy selection signal REDUN and the normal cell non-selection signal NOSEL output from the redundancy circuit are nonactive, so that data from the normal cell is transmitted to the data amplifier through the I/O line. The data amplifier outputs the data to the data bus, and the data is then transmitted to the DQ pin.
On the other hand, when the redundancy circuit is activated upon predetermined addressing, the redundancy selection signal REDUN and the normal cell non-selection signal NOSEL are activated. The data from the redundancy cell is transmitted to the data amplifier through the I/O line, is output from the data amplifier to the data bus, and is then output to the DQ pin. The redundancy selection signal REDUN is also input into the redundancy detection circuit. Since, however, the redundancy detection circuit is nonactive, the judgement result output signal REDRLT is nonactive.
Next, at the time of the roll call test, the test signal activation address signal is activated, the test signal activation circuit is activated, and the roll call test signal ROLLC is activated. Upon activation of the roll call test signal ROLLC, the data amplifier activation circuit renders the data amplifier activation signal DAMP nonactive to render the data amplifier nonactive, activates the redundancy detection circuit activation signal REDTST, and activates the redundancy detection circuit. Data from the normal cell and the redundancy cell is transmitted to the data amplifier through the I/O line. Since the data amplifier is nonactive, the data in the memory cell is not output from the data amplifier to the data bus.
When the redundancy circuit is rendered nonactive upon predetermined addressing, the redundancy selection signal REDUN and the normal cell non-selection signal NOSEL output from the redundancy circuit are nonactive, so that the redundancy detection circuit, which receives the redundancy selection signal REDUN, renders the judgement result output signal REDRLT nonactive. The judgement result output signal REDRLT is connected to the data bus, and the data in the data bus is input into the data output circuit and is output to the DQ pin.
When the redundancy circuit is activated upon predetermined addressing, the redundancy selection signal REDUN and the normal cell non-selection signal NOSEL output from the redundancy circuit are activated and respectively input into the redundancy cell and the normal cell. Since, however, the data amplifier is nonactive, the data in the memory cell is not output to the data bus. Upon receipt of the redundancy selection signal REDUN, the redundancy detection circuit activates the judgement result output signal REDRLT which is then output to the data bus. The data output circuit receives the data in the data bus and outputs the data to the DQ pin. Reference to the results output to the DQ pin permits judgement on whether or not the redundancy to be in use. To this end, presetting on the circuit should be made so that "high data" is output when the redundancy is in use, while "low data" is output when the redundancy is not in use.
The conventional roll call tester, however, requires use of a redundancy detection circuit which, upon receipt of a redundancy selection signal REDUN from a redundancy circuit, detects whether or not the redundancy is in use. A signal is also required for outputting the detection results and the like. The additional provision of the circuit and the signal line pose a problem of increased chip area.